The devices for controlling a computer system consisting in moving by means of a mouse, trackball or another pointing device, a cursor in order to indicate on the screen of the system an object, icon or element of a menu, representative of a function to be carried out, are well-known. If they were in the beginning reserved to professionals working on high range graphic consoles, they are today the symbol of the democratization of the use of the computer by removing the obligation to have to learn esoteric process control languages. Even a child not knowing yet how to read can play with a computer provided with a graphic interface.
The manufacturers of pointing devices thus sought to make those of the most possible pleasant use. A constraint, generally aggravating, is the presence of the wire connecting the mouse to the central processing unit, and being used at the same time for the transmission of the data in series mode and for the power supply. This wire is always too short or clings to the most various objects. A mouse without wire is thus regarded as an improvement.
Such a pointing device is described in the European patent application EP0171747, in the name of METAPHOR COMPUTER SYSTEMS Company, published on Feb. 19, 1986. The device transmits its displacements and the states of its command buttons to the central processing unit by means of an infrared beam of light modulated in amplitude by the sequences of representative binary digits. The implementation of an infrared base band transmission is extremely simple, but it can appear reception problems due to the ambient light, which can present spectral components in the near infrared (Sun, incandescent lamps). It was thus required an improvement of the reception by using means of concentration and guidance of the received light.
The Japanese patent application JP4205129, in the name of HITACHI LTD Company, published on Jul. 27, 1992, features such a system.
Another technical problem is set by the power supply of the wireless mouse. Suppression of the wire constraint leads to another constraint obligation to reload the battery periodically before the device ceases functioning. EP017747 application brought a partial response to this problem by transmitting to the central processing unit a message of alarm intended for the user.
The European patent application EP0849700, by the PHILIPS PATENTVERWALTUNG and PHILIPS ELECTRONICS companies, published on Jun. 24, 1998, proposes a feeding of the wireless mouse by an inductive loop placed in the mouse pad. The wire of the mouse is actually removed, but the problem is moved on the level of supplying electric power in the appropriate form to the pad. A new wire is thus necessary; moreover, the user is limited in his aesthetic choices of this accessory, since the pad is obligatorily of a model especially adapted to the system.
The power supply is not a question being asked only for pointing devices of computer. It is asked for all small electronic instruments. Generally, cells are used. The periodic replacement of those can become expensive for the user, and one uses batteries more and more commonly, at the price of a more significant starting investment, in particular in a charger. For low powers, a mixed feeding by battery and solar cell, the battery playing a role of buffer, is known since the appearance on the market of cheap amorphous silicon cells. It is the case of pocket calculators or of office calculating machines. The devices described in the Japanese patent applications JP56132653 and JP61210828, respectively in the name of SEIKO EPSON CORP and of CASIO COMPUTER CO LTD, are examples among others.
The embodiment of a solar cell power supply in a wireless mouse implementing an infrared connection is described in the British patent application GB2292995, in the name of PRIMAX ELECTRONICS LTD, published on Mar. 13, 1996.
The improvements of the basic pointing device largely known in the field of microprocessing, relate only to the individual use of an information processing system. One knows possibilities of co-operating work of several people by the setting of several central processing units connected by a network. However, even if work is collective, each person personally controls each central processing unit by means of her/his own pointing device.
A system making it possible to several people to use the same central processing unit is described in the Japanese patent applications JP8221194 and JP9146703, in the name of NTT Company, published respectively on Aug. 30, 1996 and on Jun. 6, 1997. The commands coming from several wireless mice can be received by a conventional microcomputer. To this end, a time-sharing radio transmission technique is implemented. The various mice transmit successively their data when they receive an identifying code sent by the basic station connected to the central processing unit corresponding to their own codes. The envisaged use is that of education and game.
The Japanese patent application JP10040002, in the name of NEC Company, published on Feb. 13, 1998, described simultaneous operation of several mice in the same window.
The concept of a set of pointing devices controlling a single information processing system presents interesting prospects in particular in leaching. Contrary to the teaching of other disciplines, data-processing practices lends itself currently rather badly to collective courses. The training is rather based on the setting of practical working sessions, during which the pupils, by small groups of two or three, are exerted on a complete microcomputer. To let a great number of pupils to profit from an initiation, one thus needs average considerable hardware permanently installed in specialized classrooms, having many power supply plugs.
The wireless mouse systems described above in the JP9146703, JP8221194 and JP10040002 patent documents would allow on the contrary a more traditional approach of initiation into handling of a computer. Each pupil having a mouse, could, under the control of a trainer, learn how to use a graphic interface, the image of which could be projected on a large-sized screen by means of an adapted data-processing peripheral, such as a video projector, or a LCD tablet adapted to an overhead projector.
The economic advantage is obvious: only one information processing system is enough, which could consist of a portable microcomputer. The specialized rooms are not necessary any more, and the equipment can be installed quickly in any room. However, this economic advantage is a bit limited by the complexity of the known systems. The data transmission protocols between the mice and the central processing unit rely on microwave links, which force each pointing device to comprise a receiver to receive synchronization signals. Radio links present also many disadvantages in countries where there are constraining regulations with regard to frequency bands allowed for data transmission. The number of these bands is restricted and the remaining bands are extremely encumbered, therefore the use of complex data coding methods is mandatory to avoid a disturbance by a similar system operating in the vicinity.
The recourse to an infrared link would thus seem more suitable, the channels of communication by this means inside a room being preserved from external disturbances. Moreover, the system could implement electronic components having very great diffusion, since infrared remote control systems are of universal use.
The system requires at least a number of communication channels at equal to the number of pointing devices, and must be insensitive to the ambient light, but modulation techniques having the desired characteristics exist. One can quote the frequency shift keying of a subcarrier, an example of which is given in the European patent application EP0342146, in the name of TRANSDATA Company, published on May 11, 1989. The described device relates to only one bi-directional connection between an electric meter and an apparatus intended to pick up power consumption, and the implemented method could not thus be directly applied. However, hie demodulation method described in this document, based upon cabled electronics, can be replaced easily by equivalent software processing.
The European application EP0924873, in the name of ALCATEL Company, published on Jun. 23, 1999, is describing an algorithm allowing the detection of the answering tone of modems and telecopiers.
This type of algorithm of the Goertzel type, is well known, and can apply to the detection of voice frequencies. The necessary significant computing power implies the use of dedicated digital signal processing circuits, like those manufactured by ADVANCED MICRO DEVICES Company. This company reveals besides an improvement of the Goertzel algorithm in the international patent application WO97/20438, published on Jun. 5, 1997. In the technical note “DTMF Tone Generation and Detection: An implementation Using the TMS320C54x” (Application Report; SPRA096A—May 2000), the TEXAS INSTRUMENTS Company describe algorithms to make synthesis and detection of signals in a multifrequency system.
It appears from the state of the art as described in the documents quoted above, that sets of pointing devices intended for a user group for controlling a common information processing system are known, but that there is not to date any simple, robust and cheap system relying on trusted and modern techniques, which can really be implemented in particular with a view to teaching by carrying out an inventive synthesis of the state of the art in order to obtain optimal characteristics.